1. Field of the Invention
This invention relates to an apparatus for producing fiber aggregate which is appropriate for the production of fiber reinforced metal, and more particularly to an apparatus for producing annular fiber aggregate in which most of the fibers are oriented in the peripheral tangent direction.
2. Description of the Prior Art
A basic technology has been known for obtaining fiber aggregate in which most of the fibers are oriented one-dimensionally. In the basic technology, a fiber suspension in which fibers are dispersed in a dielectric fluid is supplied in an electric field generated between a positive electrode and a negative electrode disposed in parallel, whereby the fibers are oriented electrostatically, bridged simultaneously, and the thus oriented fibers are sedimented on after another.
According to the basic technology, fiber aggregate can be obtained in which most of the fibers are oriented one-dimensionally or linearly. Although this fiber aggregate has its own applicability, there are many functional parts of annular or cylindrical shape to which the application of fiber reinforced metal has been desired strongly. However, the fiber aggregate of linearly oriented fibers cannot satisfy the quality requirements of the functional parts of annular or cylindrical shape.
An invention, disclosed in Japanese Unexamined Patent Publication No. 227853/1988 and illustrated in FIGS. 4 and 5, is intended for solving the above-mentioned problem. In the invention, electric fields are generated among a plurality of pairs of a positive electrode 5 and a negative electrode 6 disposed alternately within the upright cylindrical space 4 in the normal direction with respect to the periphery of the upright cylindrical space 4, and a fiber suspension in which discontinuous fibers such as short fibers and whiskers are dispersed in a dielectric fluid 11 is supplied in the electric fields to orient the fibers in the peripheral tangent direction and bridge the fibers simultaneously, thereby sedimenting and aggregating the thus oriented fibers one after another. While sedimenting and aggregating the oriented fibers, the positive electrodes 5 and the negative electrodes 6 are rotated gently, and the position of the positive electrodes 5 and the negative electrodes 6 is displaced successively and relatively in the longitudinal direction of the upright cylindrical space 4 to keep the clearance, formed between the bottom ends of the positive electrodes 5 and the negative electrodes 6 and the aggregated fiber layer 12, at a predetermined value.
In the above-mentioned annular fiber aggregate production technology, although the plurality of the pairs of the positive and negative electrodes 5 and 6 is formed in a circular or net shape, and rotated gently in the fiber suspension in order to orient the fibers uniformly, the rotation of the positive and negative electrodes 5 and 6 tends to adversely affect and disturb the fibers under the orientation and bridging. In addition, when the positive and negative electrodes 5 and 6 are displaced perpendicularly so as to keep the predetermined clearance between the bottom ends thereof and the sedimented and aggregated fiber layer 12, the electric fields inevitably concentrate on the bottom ends of the positive and negative electrodes 5 and 6, and the fibers adjacent to the surface of the aggregated fiber layer 12 are lifted consequently, thereby causing another disturbance to the fibers having been oriented and aggregated so far.